Guided filter with support wire and methods of use

ABSTRACT

A guided filter system for temporary placement of a filter in an artery or vein is disclosed. The system includes a guidewire slideable through a wire guide included in a distal region of a support wire. The support wire has an expandable filter, which is operable between a collapsed or enlarged condition. A variety of endovascular devices, including angioplasty, atherectomy, and stent-deployment catheters, are insertable over the guidewire and/or the support wire. Methods of using the guided filter system to direct and exchange endovascular devices to a region of interest, and to entrap and remove embolic material from the vessel are also disclosed.

This application is a continuation of U.S. patent application Ser. No.09/366,192, filed on Aug. 3, 1999 now U.S. Pat. No. 6,142,987.

FIELD OF THE INVENTION

The present invention relates generally to devices and methods forproviding temporary placement of a filter in a blood vessel. Moreparticularly, the invention provides a guidewire system for entrapmentof embolic material in an artery or vein during an endovascularprocedure. The system also provides a support wire for directing and/orexchanging other “over the wire” devices, such as angioplasty,atherectomy, or stent deployment catheters, to a region of interestwithin the vessel.

BACKGROUND OF THE INVENTION

Treatment of thrombotic or atherosclerotic lesions in blood vesselsusing an endovascular approach has recently proven to be an effectiveand reliable alternative to surgical intervention in selected patients.For example, directional atherectomy and percutaneous translumenalcoronary angioplasty (PTCA) with or without stent deployment are usefulin treating patients with coronary occlusion. Atherectomy physicallyremoves plaque by cutting, pulverizing, or shaving in atheroscleroticarteries using a catheter-deliverable endarterectomy device. Angioplastyenlarges the lumenal diameter of a stenotic vessel by exertingmechanical force on the vascular walls. In addition to usingangioplasty, stenting, and/or atherectomy on the coronary vasculature,these endovascular techniques have also proven useful in treating othervascular lesions in, for example, carotid artery stenosis, peripheralarterial occlusive disease (especially the aorta, the iliac artery, andthe femoral artery), renal artery stenosis caused by atherosclerosis orfibromuscular disease, superior vena cava syndrome, and occlusive iliacvein thrombosis resistant to thrombolysis.

It is well recognized that one of the complications associated withendovascular techniques is the dislodgment of embolic materialsgenerated during manipulation of the vessel, thereby causing occlusionof the narrower vessels downstream and ischemia or infarct of the organwhich the vessel supplies. In 1995, Waksman et al. disclosed that distalembolization is common after directional atherectomy in coronaryarteries and saphenous vein grafts. See Waksman et al., American HeartJournal 129(3): 430-5 (1995), incorporated herein by reference. Thisstudy found that distal embolization occurs in 28% (31 out of 111) ofthe patients undergoing atherectomy. In January 1999, Jordan, Jr. et al.disclosed that treatment of carotid stenosis using percutaneousangioplasty with stenting is associated with more than eight times therate of nicroemboli seen using carotid endarterectomy. See Jordan, Jr,et al. Cardiovascular surgery 7(1): 33-8 (1999), incorporated herein byreference.

Microemboli, as detected by transcranial Doppler monitoring in thisstudy, have been shown to be a potential cause of stroke. The embolicmaterials include calcium, intimal debris, atheromatous plaque, thrombi,and/or air.

There are a number of devices designed to provide blood filtering forentrapment of vascular emboli. The vast majority of these devices aredesigned for permanent placement in veins to prevent pulmonary embolism.A temporary venous filter device is disclosed in Bajaj, U.S. Pat. No.5,053,008 (this and all other references cited herein are expresslyincorporated by reference as if fully set forth in their entiretyherein). The Bajaj device is an intracardiac catheter for temporaryplacement in the pulmonary trunk of a patient predisposed to pulmonaryembolism due to, e.g., hip surgery, major trauma, major abdominal orpelvic surgery, or immobilization. The Bajaj device includes an umbrellamade from meshwork which traps venous emboli before they reach thelungs. This device is designed for venous filtration and is not suitablefor arterial use because of the hemodynamic differences between arteriesand veins.

There are very few intravascular devices designed for arterial use.Arteries are much more flexible and elastic than veins and, in thearteries, blood flow is pulsatile with large pressure variations betweensystolic and diastolic flow. These pressure variations cause the arterywalls to expand and contract. Blood flow rates in the arteries vary fromabout 1 to about 5 L/min. Ginsburg, U.S. Pat. No. 4,873,978, disclosesan arterial filtering system, which includes a catheter with a strainerdevice at its distal end. This device is inserted into the vesseldownstream from the treatment site and, after treatment, the strainer iscollapsed around the entrapped emboli and removed from the body. TheGinsburg device could not withstand flow rates of 5 L/min. It isdesigned for only small arteries and therefore could not capture embolidestined for all parts of the body. Ing. Walter Hengst GmbH & Co, GermanPatent DE 34 17 738, also discloses another arterial filter having afolding linkage system which converts the filter from the collapsed tothe expanded state.

Filters mounted to the distal end of guidewires have been proposed forintravascular blood filtration. A majority of these devices includes afilter which is attached to a guidewire and is mechanically actuated viastruts or a pre-shaped basket which deploys in the vessel. These filtersare typically mesh “parachutes” which are attached to the shaft of thewire at the distal end and to wire struts which extend outward in aradial direction at their proximal end. The radial struts open theproximal end of the filter to the wall of the vessel. Blood flowingthrough the vessel is forced through the mesh thereby capturing embolicmaterial in the filter. These devices are self-directing and can beplaced intravascularly. However, one major disadvantage associated withthe current devices is that the steerability of the guidewire may bealtered as compared to the conventional guidewires due to the size ofthe filter. The guidewire may bend, kink, and/or loop around in thevessel, making insertion of the filter through a complex vascular lesiondifficult.

During endovascular procedures, it is not uncommon to exchange oneendovascular device for another over the guidewire. However, theguidewire position is often lost or compromised during the exchange ofdevices. For example, during coronary revascularization, it is oftenrequired to exchange of one guide catheter for another guide catheterpossessing different qualities, e.g., a larger diameter guide to delivera specialized angioplasty device, a smaller diameter guide to preventdeep intubation and/or pressure damping, a different guide shape, or aguide catheter containing side holes. It is known that there are fewinterventional maneuvers as challenging as attempting to maintain distalguidewire access while trying to exchange one guiding catheter foranother without compromising the guidewire position.

What is needed are simple and safe blood filtering and guidewire systemswhich can be temporarily placed in the arteries and veins to preventdistal embolization during endovascular procedures, and can be used tointroduce and/or exchange various instruments to a region of interestwithout compromising the position of the filter or guidewire. Existingdevices are inadequate for this purpose.

SUMMARY OF THE INVENTION

The present invention provides devices and methods for introduction ofendovascular devices, e.g., guide catheters, atherectomy catheters,angioplasty catheters, intravascular ultrasound catheters, orstent-deployment catheters, and for protecting a patient from distalembolization during cardiovascular procedures. More specifically, aguided filter system with support wire is disclosed for capturingembolic material generated during the procedure and for directing orexchanging other devices to a region of interest in an artery or vein.

In one embodiment, the filter system comprises a guidewire and a supportwire having an expandable filter, e.g., a parachute, basket, or scroll,mounted on a distal region of the support wire. The support wire isadapted for percutaneous insertion into an artery or vein and is adaptedto receive an endovascular instrument. The distal region of the supportwire includes a wire guide, which slideably engages the guidewire. Incertain embodiments, the wire guide comprises a ring having an apertureadapted to receive the guidewire.

In another embodiment, the filter comprises an expansion frame and amesh disposed over the frame. The filter can be placed in a collapsedcondition to facilitate entry into a vessel and an enlarged condition tocapture embolic material in the vessel. In certain embodiments, theframe comprises a plurality of struts bonded to the guidewire at a firstend, and the struts expand radially outward at a second end. Theconstruction and use of expansion means and associated filter mesh havebeen thoroughly discussed in earlier applications including Barbut etal., U.S. application Ser. No. 08/533,137, filed Nov. 7, 1995, Barbut etal., U.S. application Ser. No. 08/580,223, filed Dec. 28, 1995, Barbutet al., U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996, Barbutet al., U.S. application Ser. No. 08/640,015, filed Apr. 30 1996, Barbutet al., U.S. application Ser. No. 08/645,762, filed May 14, 1996, andBarbut et al., U.S. Pat. No. 5,662,671, and the contents of each ofthese prior applications are expressly incorporated herein by reference.

The methods of the present invention include deployment of apercutaneous medical instrument during an endovascular procedure toremove plaque and/or thrombi from the coronary artery, aorta, commoncarotid artery, external and internal carotid arteries, brachiocephalictrunk, middle cerebral artery, basilar artery, subclavian artery,brachial artery, axillary artery, iliac artery, renal artery, femoralartery, popliteal artery, celiac artery, superior mesenteric artery,inferior mesenteric artery, anterior tibial artery, posterior tibialartery, and all other arteries carrying oxygenated blood. The methodsalso include prevention of distal embolization during an endovascularprocedure to remove thrombi and/or foreign bodies in the venouscirculation, including the superior vena cava, inferior vena cava,external and internal jugular veins, brachiocephalic vein, pulmonaryartery, subclavian vein, brachial vein, axillary vein, iliac vein, renalvein, femoral vein, profunda femoris vein, great saphenous vein, portalvein, splenic vein, hepatic vein, and azygous vein.

In a first method of using the guided filter system, the distal end ofthe guidewire is inserted percutaneously through an artery or vein andadvanced into or beyond a region of interest, typically a stenoticlesion caused by buildup of atherosclerotic plaque and/or thrombi. In acollapsed condition, the filter and the distal region of the supportwire are advanced over the guidewire, having the wire guide of thesupport wire engaging the guidewire, i.e., like a monorail catheterengaging a guidewire. The filter is expanded downstream of the vascularocclusion, and the guidewire is withdrawn and removed from the body. Thedistal region of an endovascular device, such as an atherectomy,stent-deployment, or angioplasty catheter, is inserted over the supportwire and advanced to the region of interest. After the stenotic lesionis removed or otherwise treated by the endovascular device and anadequate lumenal diameter is established, the filter is collapsed andremoved, together with the captured embolic debris, from the vessel bywithdrawing the support wire.

In another method, after the guidewire and the support wire with theexpanded filter are positioned in a vessel distal to the region ofinterest, the endovascular device is inserted over both the guidewireand the support wire to position within the region of interest. Duringcertain cardiovascular procedures, especially coronaryrevascularization, exchange of endovascular instruments and catheters isneeded and is difficult to accomplish because the initial guidewirepositioning across the region of interest is often lost as the firstdevice is withdrawn. Using the guided filter system, the guidewire andthe support wire are both advanced distal to the region of interest. Ifthe position of the guidewire is lost during the withdrawal of the firstdevice, the second device that needs to be exchanged can be advancedover the support wire to be positioned within the region of interest.

It will be understood that there are several advantages in using thedevices and methods disclosed herein for capturing and removing embolicdebris during endovascular procedures. For example, the guided filtersystem (1) is particularly well suited for temporary filtration of bloodin any vessel to entrap embolic debris, thereby minimizing neurologic,cognitive, and cardiac complications associated with distalembolization, (2) can withstand high arterial blood flow for an extendedtime, (3) includes a mesh that is sufficiently porous to allow adequateblood flow in a blood vessel while capturing emboli, (4) can be used todirect an endovascular catheter to a region of interest in the vessel,(5) can be used to exchange medical instruments without compromising theposition of the guidewire, and (6) can be used in adult and pediatricpatients.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts an embodiment of a support wire having a filter in acollapsed condition according to the present invention.

FIG. 1B depicts the support wire of FIG. 1A having the filter in anexpanded condition.

FIG. 1C depicts a cross-sectional view through section line C—C of thesupport wire depicted in FIG. 1B.

FIG. 1D depicts the support wire of FIG. 1C having a guidewire receivedthrough the wire guide mounted within the filter.

FIG. 1E depicts the support wire of FIG. 1C having a guidewire receivedthrough the wire guide mounted proximal to the filter.

FIG. 1F depicts the support wire of FIG. 1C having a guidewire receivedthrough the wire guide mounted distal to the filter.

FIG. 1G depicts the guidewire and the support wire carried within arapid exchange catheter.

FIG. 1H depicts the catheter of FIG. 1G deployed over an atheromatouslesion in a vessel.

FIG. 1I depicts the guidewire and the support wire carried within arapid exchange catheter.

FIG. 1J depicts the guidewire and the support wire carried within arapid exchange catheter.

FIG. 1K depicts the guidewire and the support wire carried within arapid exchange catheter.

FIG. 2A depicts an embodiment of a distal end of the guidewire.

FIG. 2B depicts an alternative embodiment of the distal end of theguidewire.

FIG. 2C depicts another alternative embodiment of the distal end of theguidewire.

FIG. 3A depicts another embodiment of the filter shaped as a parachute.

FIG. 3B depicts another embodiment of the filter shaped as an eggbeater.

FIG. 4A depicts a guidewire inserted across a vascular occlusion.

FIG. 4B depicts the filter and support wire engaging the guidewire withthe filter expanded beyond the vascular occlusion.

FIG. 4C depicts an angioplasty catheter inserted over the support wire.

FIG. 4D depicts an angioplasty catheter inserted over the guidewire andthe support wire.

DETAILED DESCRIPTION

In a first embodiment, a filter system for temporary placement in avessel, either an artery or vein, is provided as depicted in FIGS. 1A,1B, 1C, and 1D. The filter system includes support wire 10 having aproximal end, distal region 11, and expandable filter 20 mounted at thedistal region. The filter comprises expansion frame 22 and mesh 25 whichis sonic welded or adhesive bonded to struts 28 of the expansion frame.Anticoagulants, such as heparin and heparinoids, may be applied to mesh25 to reduce thrombi formation on the mesh. The filter can be collapsedas shown in FIG. 1A to facilitate insertion into a vessel, andthereafter expanded as shown in FIG. 1B. Wire guide 26 is included indistal region 11 of the support wire. The wire guide may be mountedwithin the filter (as shown in FIG. 1B and FIG. 1C) or at any othersuitable position on support wire 10 proximal of the filter (as shown inFIG. 1E), or on a distal extension of the support wire which extendsbeyond the filter (as shown in FIG. 1F). In certain embodiments, thesupport wire may comprise a ring. A cross-sectional view of the supportwire through section line C—C is depicted in FIG. 1C. The design andconstruction of a variety of filters for use on guidewire is describedin detail in Tsugita et al., U.S. Pat. No. 5,911,734, the disclosure ofwhich is expressly incorporated herein by reference in its entirety.

In another embodiment, the filter further includes a capture sheathwhich covers the filter and is removeable from the filter, the sheathhaving a port in its distal region adapted to receive the guidewire inthe manner of a rapid exchange catheter. In FIG. 1G, support wire 10 isinserted in lumen 51 of a rapid exchange catheter 50. The catheterincludes side port 60 in its distal region, adapted to receive guidewire30. In FIG. 11, the catheter includes skive 61 which receives guidewire30. In FIG. 1J, elongate member 70 carries tubular segment 75 havingskive 77 at a distal region of elongate member 70. The tubular segmentacts as a capture sheath for the filter while the skive receives theguidewire. In FIG. 1K, elongate member 70 carries first and secondtubular segments, 75 and 79, adapted to receive, respectively, thefilter and the guidewire.

When in use, guidewire 30 is first inserted into a vessel and advanceddistal to the region of interest. The catheter, which carries the filterin lumen 51, is inserted over the guidewire, the guidewire engagedthrough side port 60. The filter is advanced distally passingatheromatous lesion 100. The guidewire can then be withdrawn andcatheter 50 drawn proximal, leaving the catheter and the filter insertedin the vessel as depicted in FIG. 1H. Catheter 50 is then removed fromthe vessel. Expansion frame 22 is expanded to capture embolic materialsdownstream the atheromatous lesion. An endovascular device, such as anangioplasty catheter with or without a stent, can be inserted oversupport wire 10 to position adjacent atheroma 100. After vascularprocedures are performed with the endovascular device(s), the device(s)are withdrawn and removed from the vessel. The filter with the capturedemboli is then contracted and removed.

The filter system also includes guidewire 30 having a proximal end anddistal end 33. The guidewire is slideably received by support wire 10through wire guide 26 as depicted in FIG. 1D. The filter system furtherincludes endovascular devices, such as atherectomy catheters,endovascular imaging devices, stent-deployment catheters, angioplastycatheters, pressure monitors, electrophysiology catheters, andaspirators, which are adapted to receive guidewire 30 and/or supportwire 10 in their lumens.

Different constructions of distal end 33 of the guidewire are depictedin FIGS. 2A, 2B, and 2C. Distal end 33 may assume a substantially linearconfiguration relative to the proximal end of the guidewire as depictedin FIG. 2A. Alternatively, distal end 33 may assume an angularconfiguration relative to the proximal end of the guidewire as depictedin FIG. 2A. Distal end 33 may be shaped like a fishhook as depicted inFIG. 2C. The distal region of the guidewire may be constructed of aflexible material to facilitate entry through a region of interest, andpreferably is equipped with an atraumatic tip as is known in the art.The embodiments in FIGS. 2B and 2C, having a curvilinear design, areparticularly useful in achieving access to a complex lesion in atortuous vessel.

FIGS. 3A and 3B depict alternative embodiments of expandable filter 20mounted on the distal region of support wire 10. In FIG. 3A, filter 20comprises a parachute frame, and mesh 25 which is welded (e.g., sonic orlaser) or adhesive bonded to struts 28. Wire guide 26 is included in thedistal region of the support wire and projects distally from filter 20for engaging a guidewire. In FIG. 3B, filter 20 comprises compressiblestruts 22, and mesh 25. In an expanded condition, filter 20 assumes theshape of an eggbeater.

By way of example, when the filter system as disclosed herein isintended for use in the aorta, the area of the mesh required for thedevice is calculated from Bemoulli's equation as described in ourearlier applications including Barbut et al., U.S. application Ser. No.,U.S. application Ser. No. 08/553,137, filed Nov. 7, 1995, Barbut et al.,U.S. application Ser. No. 08/580,223, filed Dec. 28, 1995, Barbut etal., U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996, Barbut etal., U.S. application Ser. No. 08/640,015, filed Apr. 30, 1996, andBarbut et al., and U.S. application Ser. No. 08/645,762, filed May 14,1996, all of which are incorporated herein by reference.

In an embodiment of the guided filter system that is to be used in theaorta, mesh with dimensions within the following ranges is desirable:mesh area is 0.004-5 in², more preferably 0.007-4 in², more preferably0.010-3 in², more preferably 0.015-2 in², more preferably 0.020-1 in²,more preferably 0.025-0.076 in²; mesh thickness is 60-280 μm, morepreferably 70-270 μm, more preferably 80-260 μm, more preferably 90-250μm, more preferably 100-250 μm, more preferably 120-230 μm, morepreferably 140-210 μm; thread diameter is 30-145 μm, more preferably40-135 μm, more preferably 50-125 μm, more preferably 60-115 μm, morepreferably 70-105 μm, and pore size is 500 μm or less, more preferably400 μm or less, more preferably 300 μm or less, more preferably 200 μmor less, more preferably 100 μm or less, more preferably 50 μm or lessand usually larger than at least a red blood cell. In a preferredembodiment of the invention, mesh area is 2-8 in², mesh thickness is60-200 μm, thread diameter is 30-100 μm, and pore size is 50-300 μm. Ina further preferred embodiment of the invention, mesh area is 3-5 in²,mesh thickness is 60-150 μm, thread diameter is 50-80 μm, and pore sizeis 100-250 μm. In other embodiments, the filter comprises a thin filmlaser cut with holes to allow blood flow. Typical dimensions includepore size of 20-500 μm, a thickness of 0.0005-0.003 inches, and areaapproximately same as for meshes described above.

In other embodiments, the filter comprises a thin film laser cut withholes to allow blood flow. Typical dimensions include pore size of20-500 μm, a thickness of 0.0005-0.003 inches, and area approximatelysame as for meshes described above.

Once appropriate physical characteristics are determined, suitable meshcan be found among standard meshes known in the art. For example,polyester meshes may be used, such as meshes made by Saati Corporationsand Tetko Inc. These are available in sheet form and can be easily cutand formed into a desired shape. In a preferred embodiment, the mesh iswelded (e.g. sonic or laser) or sewn into a cone shape. Other meshesknown in the art, which have the desired physical characteristics, arealso suitable. Anticoagulants, such as heparin and heparinoids, may beapplied to the mesh to reduce the chances of blood clotting on the mesh.Anticoagulants other than heparinoids also may be used, e.g., monoclonalantibodies such as ReoPro (Centocor). The anticoagulant may be paintedor sprayed onto the mesh. A chemical dip comprising the anticoagulantalso may be used. Other methods known in the art for applying chemicalsto mesh may be used.

In use, as depicted in FIG. 4A, guidewire 30 is inserted percutenouslythrough a peripheral artery or vein and advanced typically in thedirection of blood flow. However, guidewire 30 may be inserted andadvanced in a direction opposite the blood flow, e.g., retrogradethrough the descending aorta to reach the coronary artery. Distal end 33of the guidewire is passed through occluding lesion 100, typically anatheromatous plaque, and positioned distal to the occlusion. Supportwire 10 of FIG. 1A is inserted over the proximal end of guidewire 30through wire guide 26, and advanced distally until filter 20 ispositioned distal to plaque 100 as depicted in FIG. 4B. By having wireguide 26 engage the guidewire, the filter and the support wire can beeasily steered intravascularly to reach the region of interest. Filter20 is expanded to capture embolic material, such as calcium, thrombi,plaque, and/or tissue debris. Guidewire 30 is then withdrawn, leavingsupport wire 10 in position to direct an endovascular device to plaque100.

Percutaneous translumenal angioplasty has been successful in treatingarterial stenoses as well as occlusive venous thrombosis resistant tothrombolysis. See American Heart Journal, 125 (2 Pt 1): 362-6 (1993).Angioplasty catheter 40, which has angioplasty balloon 42 mounted on thedistal region, is inserted over support wire 10 as depicted in FIG. 4C.In a deflated state, the angioplasty balloon is advanced over supportwire 10 to a position adjacent plaque 100. The atheromatous plaque iscompressed by inflating balloon 42, thereby dilating the stenosis in thevessel. In certain embodiments, the angioplasty catheter includesinfusion port 44 proximal and perfusion port 45 distal to balloon 42.Infusion port 44 may be used to administer pharmaceutical agents, e.g.,t-PA, adenosine, or nitroglycerin through the catheter lumen (notshown). Oxygenated medium or blood may be infused through port 45 tomaintain perfusion to distal organs during angioplasty. In certainembodiments, a stent is closely associated with the angioplasty balloon.The stent is typically crimped onto the balloon and is capable ofcontrolled radial expansion in the region of interest upon applicationof a radial, outwardly extending force from the interior of the stent.The construction of the catheter system carrying a stent is described indetail in Jang et al., U.S. Pat. No. 5,749,848, which is incorporatedherein by reference in its entirety.

The angioplasty catheter or other endovascular instrument is withdrawnfrom the vessel after completion of angioplasty. Embolic materialgenerated during the angioplasty is captured and retained by filter 20.The filter is then contracted, and with captured embolic material, iswithdrawn from the vessel and removed from the patient's body.

Alternatively, after filter 20 is positioned and expanded distal toplaque 100, guidewire 30 and support wire 10 may remain in the vesselacross plaque 100 as depicted in FIG. 4D. Angioplasty catheter 40 isthen inserted over both guidewire 30 and support wire 10 to a positionadjacent plaque 100. If an atherectomy device, for example, is requiredto remove plaque remaining after angioplasty, angioplasty catheter 40 iswithdrawn, with or without the guidewire, and an atherectomy catheter isinserted over guidewire 30 and/or support wire 10 to a position adjacentthe plaque. In this way, if the position of guidewire 30 across theplaque is lost during the removal of angioplasty catheter 40, supportwire 10 is available to direct another endovascular device to the regionof interest. This method is particularly useful for exchanging guidecatheters during coronary revascularization.

The length of the guidewire and the support wire will generally bebetween 30 and 300 centimeters, preferably approximately between 50 and180 centimeters. The filter will be capable of expanding to an outerdiameter of at least 0.2 centimeters, more preferably at least 0.5centimeters, more preferably at least 1.0 centimeters, more preferablyat least 1.5 centimeters, more preferably at least 2.0 centimeters, morepreferably at least 2.5 centimeters, more preferably at least 3.0centimeters, more preferably at least 3.5 centimeters, more preferablyat least 4.0 centimeters, more preferably at least 4.5 centimeters, morepreferably at least 5.0 centimeters. These ranges cover suitablediameters for both pediatric and adult use. The foregoing ranges are setforth solely for the purpose of illustrating typical device dimensions.The actual dimensions of a device constructed according to theprinciples of the present invention may obviously vary outside of thelisted ranges without departing from those basic principles.

Although the foregoing invention has, for the purposes of clarity andunderstanding, been described in some detail by way of illustration andexample, it will be obvious that certain changes and modifications maybe practiced which will still fall within the scope of the appendedclaims. Moreover, it will be understood that each and every featuredescribed for any given embodiment or in any reference incorporatedherein, can be combined with any of the other embodiments describedherein.

What is claimed is:
 1. A percutaneous filter system, comprising: aguidewire; a support-wire having a proximal end, a distal end, a distalregion, and an expandable filter mounted on the distal region of thesupport wire, the support wire adapted to receive a percutaneous medicalinstrument; and a sheath which removeably covers the distal end of thesupport wire and the filter, the sheath having a proximal end, a distalend, a distal region, and a lumen extending therethrough, which receivesthe filter and an aperture adapted to pass the guidewire, wherein,during use, the guidewire is positioned in a vessel at a region ofinterest, the sheath carrying the support wire is advanced along theguidewire until the filter reaches the region of interest, and thesheath is withdrawn to expose the filter.
 2. The percutaneous filtersystem of claim 1, wherein the sheath comprises a catheter and theaperture adapted to pass the guidewire comprises a skive port positionedin the distal region of the sheath.
 3. The percutaneous filter system ofclaim 1, wherein the sheath comprises a catheter and the apertureadapted to pass the guidewire comprises a cylindrical segment secured tothe distal region of the sheath.
 4. The percutaneous filter system ofclaim 1, further comprising an elongate member having a distal end and aproximal end, the sheath carried at the distal end of the elongatemember, the aperture adapted to pass the guidewire comprising a skiveport positioned in the distal region of the sheath.
 5. The percutaneousfilter system of claim 1, further comprising an elongate member having adistal end and a proximal end, the sheath carried at the distal end ofthe elongate member, the aperture adapted to pass the guidewirecomprising a cylindrical segment secured to the distal region of thesheath.
 6. The percutaneous filter system of claim 1, wherein theaperture communicates with the lumen of the sheath.
 7. The percutaneousfilter system of claim 1, wherein the aperture is located about 10centimeters from the distal end of the sheath.
 8. A method for deployinga percutaneous medical instrument, comprising steps of: providing aguidewire, a support wire, and a sheath, the support wire having anexpandable filter mounted on the distal region, the sheath covering theexpandable filter; advancing the guidewire into a region of interestwithin a vessel; advancing the sheath and the support wire along theguidewire with the sheath engaging the guidewire; withdrawing the sheathfrom the expandable filter; expanding the filter downstream of theregion of interest; and advancing the percutaneous medical instrumentover the support wire and positioning the medical instrument within theregion of interest.
 9. The method of claim 8, wherein the sheath engagesthe guidewire through an aperture in a distal region of the shealth. 10.The method of claim 8, wherein the step of withdrawing the sheath fromthe expandable filter comprises retracting the sheath proximally. 11.The method of claim 8, wherein the step of withdrawing the sheath fromthe expandable filter comprises advancing the sheath distally.
 12. Themethod of claim 8, further comprising the step of removing the sheathfrom the vessel.